JPH0721541Y2 - Setter for firing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a firing setter that is inserted between a product to be fired and a support in a firing furnace in order to avoid a reaction between them.

[Prior Art] Magnetic materials such as ferrite used for electronic parts are manufactured by powder metallurgy. The manufacturing method of ferrite will be described below.

First, for example, Fe ₂ O ₃ (iron oxide), BaCO ₃ and SrCO ₃ are mixed at a predetermined ratio, and then this mixed raw material is pre-baked.

Next, after the calcinated mixed raw material is pulverized into a powder, the powdered raw material (hereinafter referred to as calcinated powder) is molded into a predetermined shape. In this case, in order to perform dry pressure molding, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), polyethylene glycol, and other organic compounds are added to the calcined powder as binders and lubricants to form aggregates. Adjust.

Next, this molded body is sintered in a sintering furnace to obtain a sintered product. Then, the sintered product is polished. In particular, since the firing shrinkage of ferrite is 10 to 20%, if the product has strict dimensional tolerance, finish with abrasive grains or a diamond grindstone. This completes the ferrite product.

The following reactions proceed in the firing furnace.

BaCO ₃ + 6Fe ₂ O ₃ → BaO ・ 6Fe ₂ O ₃ + CO ₂ ↑… (1) SrCO ₃ + 6Fe ₂ O ₃ → SrO ・ 6Fe ₂ O ₃ + CO ₂ ↑… (2) The reaction shown in the second equation is It is performed at a temperature of about 700 ° C or higher.

Currently, for magnetic materials such as ferrite, high-purity fine powder is used according to the required performance. For example,
The particle size of iron oxide, which is the main component, is extremely fine, 0.5 to 1.0 μm. Also, the magnetic properties of ferrite products change significantly depending on the state of main component elements, trace amounts of additives, and the atmosphere during the sintering process. For example, the secular change characteristic of magnetic permeability can also be made to have a desired characteristic by controlling the atmosphere during the sintering process.

In the firing step, it is necessary to completely burn the binder (binder) used when forming the calcined powder, and therefore the oxygen concentration in the sintering furnace is controlled. Usually, deformation of the fired product occurs due to the non-uniformity of binder loss (combustion).

The organic compound used as a binder starts to decompose at a temperature of about 400 ° C. and releases CO ₂ , CO, H ₂ O and the like, and as a result, free carbon remains on the substrate. Then, when the oxygen can penetrate into the pores of the substrate, the free carbon starts to burn. In this case, to burn carbon,
It is necessary to supply sufficient oxygen into the substrate. Also, the combustion of carbon must be finished before the sintering of the green body begins. That is, it is necessary that sufficient oxygen be present in the atmosphere surrounding the product to be fired. In particular, with respect to ferrite, which has a large shrinkage rate at the firing temperature, if the oxygen concentration in the atmosphere is not uniform, the sintered product is deformed. Conventionally, when deformation occurs, as described above, a grinding process such as polishing is performed in a post process.

At present, a single furnace, a continuous furnace, a semi-continuous furnace, and the like are used as a firing furnace used in the ferrite sintering process.
An article to be fired formed into a predetermined shape is loaded into these sintering furnaces and fired. In this case, the product to be fired of ferrite is placed on a support, charged into a furnace, and
Exposed to a high temperature atmosphere of 1300 ℃. At this time, the support supporting the article to be fired is also exposed to this high temperature atmosphere.
Therefore, it is not possible to use a support made of a material that has a low strength at high temperature and cannot support a fired product of ferrite. Usually, a ceramic plate made of Al ₂ O ₃ and SiO ₂ is used as the support.

By the way, in the sintering step, the product to be fired may react with the components of the support such as a shelf plate, resulting in defective firing. Therefore, a setter may be interposed between the support and the product to be fired. In this case, a ceramic plate made of ZrO ₂ is conventionally used as a setter because it has low reactivity.

[Problems to be solved by the invention] However, the setter made of ZrO ₂ has a problem that the material cost is high. Therefore, a low cost setter is desired.

The present invention has been made in view of such problems,
An object of the present invention is to provide a firing setter having a low material cost.

[Means for Solving the Problems] A firing setter according to the present invention forms a linear row of ceramics in a loop shape on a plane and shifts the loop centers from each other to form a loop row. Is arranged in a direction along the plane, and one to three layers of the loop layer are arranged in a direction orthogonal to the plane.

[Operation] In the present invention, the setter is configured by combining the loop-shaped ceramic linear bodies. Therefore, the material cost of the setter of the present invention is lower than that of the conventional plate-shaped setter.

Since the setter is placed on a support such as a shelf board and is interposed between the material to be fired and the support, strength is not required. That is, the setter need only have the strength required for handling. Therefore, the number of loop layers is 4
If the number of layers is more than one, not only is it wasteful, but also the material cost is increased. Therefore, the number of loop layers is 1 to 3.
Layer.

Further, since the setter according to the present invention is made of ceramic, it has excellent high temperature resistance. As the ceramic, for example, cordierite, which is relatively inexpensive, can be used. In this case, the composition of cordierite has an Al ₂ O ₃ content of 30 to 40% by weight and a SiO ₂ content of 4%.
It is preferable that the content is 5 to 57% by weight and the MgO content is 10 to 17% by weight. If the contents of Al ₂ O ₃ , SiO ₂ and MgO deviate from these ranges, the expansion coefficient and thermal conductivity of the ceramic linear body deteriorate, and the performance as a setter deteriorates.

Further, the loop-shaped linear body that constitutes the setter of the present invention has a bulk specific gravity of 0.8 to 1.2 when the wire diameter is 0.8 to 3.0 mm.
mm is preferred. The porosity at this time is 61.5 to
42%. If the bulk specific gravity is less than 0.8, the strength of the setter is low and problems such as damage during handling are likely to occur. On the other hand, when the bulk specific gravity exceeds 1.2, the air permeability is deteriorated, and unevenness of oxidation occurs, which significantly impairs the performance of the setter.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a plan view showing a setter according to an embodiment of the present invention.

The setter 12 of this embodiment is manufactured as follows. First, the kneaded ceramic material is extruded linearly from the nozzle of the extruder, the linear member 10 is placed on a flat surface while rotating the nozzle, and the nozzle is linearly moved in the direction indicated by the arrow in FIG. Move to. As a result, a loop row 11 having a shape in which a plurality of loops whose chain centers are displaced from each other in the direction of the arrow is chained is obtained. In this way
After arranging a plurality of loop rows 11 along one plane with their row directions parallel to each other, another plurality of loop rows 11 are similarly laminated and arranged. In this case, the loop row of the upper layer is placed on the loop row of the lower layer so that the center of each loop is shifted by the radius of the loop in the direction orthogonal to the row direction with respect to the loop row of the lower layer. I will do it. Further, the number of laminated layers is 3 or less. In this way, a predetermined skeleton shape is formed in which the loop rows 11 are arranged in the direction along the arrangement plane and the direction (stacking direction) orthogonal thereto. After that, the ceramic structure is cut into a predetermined shape, dried, and then fired to obtain the setter 12 having a predetermined shape.

In this embodiment, the linear body 10 is made of cordierite. The composition of this cordierite is as follows:
Shown in the table. In addition, the characteristics of this cordierite are
Shown in the table. However, the unit of the numerical values shown in Table 1 is% by weight.

In this embodiment, the loop-shaped ceramic linear bodies are arranged on the plane in this manner, and since the structure has a high porosity arranged in the thickness direction, the structure is higher than that of a conventional setter made of a ZrO ₂ plate. And if the materials are the same, the material cost is about
It becomes 1/2, which is extremely low, about 1/100 when composed of other materials. Further, since oxygen in the atmosphere is also supplied from below the article to be fired, firing failure can be suppressed.
In addition, using the setter according to the present embodiment, the temperature in the furnace is 95
The article to be fired was fired at 0 ° C. As a result, no inconvenience such as breakage of the setter occurred, and the state of the fired product after firing was good.

[Effects of the Invention] As described above, according to the present invention, the setter is configured by arranging the ceramic linear bodies having a predetermined wire diameter in the number of layers of 3 or less, so that the material cost can be reduced as compared with the conventional one. It can be significantly reduced. Further, since it has excellent air permeability, it also has an effect of suppressing firing failure.

[Brief description of drawings]

FIG. 1 is a plan view showing a setter according to an embodiment of the present invention. 10; linear body, 11; loop row, 12 ,; setter

Claims (1)

[Scope of utility model registration request] 1. A structure in which a ceramic linear body is formed into a loop shape on a plane and the loop centers are offset from each other to form a loop row, and the loop row is arranged in a direction along the plane. A firing setter having a loop layer, wherein one to three layers of the loop layer are arranged in a direction orthogonal to the plane.